An organic electroluminescent device (hereinafter, occasionally referred as “an organic EL device”) has been utilized in a display apparatus. In addition to properties such as high luminance (brightness), high light emission, full-colored display and durability, the organic EL device requires heat resistance (thermostability) because the device generates a large amount of heat when driving. In particular, when the organic EL device is used for interior lighting application and the like, it is predicted that a large amount of Joule heat is generated. Moreover, in the application such as an in-vehicle display, heat resistance is an important element because the surroundings may be exposed to high temperature. In this way, according to expansion of application of an organic EL device, it is practically important to improve heat resistance of an organic EL device.
An organic thin layer used for an organic EL device is usually an amorphous glass state from the viewpoint of mold-processability. Moreover, in order to make a device having high heat resistance, it is necessary to use an organic material having a high glass transition temperature for forming a thin layer.
Regarding a material for an organic EL device, before now, some kinds of materials forming an amorphous glass have been reported. However, inmost of these amorphous materials, a glass transition temperature (Tg) thereof is low and not more than or about 150° C. For example, as a hole-transporting material, compounds represented by the formulae (2a) to (2f) described below and having Tg of 75 to 151° C. have been proposed. As an electron-transporting material, compounds represented by the formulae (3a) to (3c) described below and having Tg of 107 to 136° C. have been proposed. Moreover, as a light emissive material, compounds represented by the formulae (4a) to (4c) described below and having Tg of 84 to 132° C. have been proposed. Incidentally, the inventors of the present invention found the compounds (2a) to (2f), (3a) to (3c) and (4a) to (4c).

Since these materials have low glass transition temperatures, it is difficult to improve heat resistance of organic EL devices obtained from these materials. Moreover, mold-processability is insufficient in these materials.
As a material for a polymeric organic EL device, there have been known a main chain-type polymer having a π-electron system in a main chain thereof, or a side chain-type polymer having a π-electron system in a side chain thereof. These materials are excellent in mold-processability. The main chain-type polymer, for example, includes materials represented by the following formulae.

On the other hand, the side chain-type polymer has diversity of choices in a π-electron system chromophore constituting a side chain, and has superior chemical stability. Further, since an unconjugated-system structure in the side chain-type polymer is easily made in a main chain thereof, it is easy to impart mold-processability to the polymer. Moreover, the polymer has advantages such as excellent photoconductivity, and constant standard oxidation-reduction potential independent of doping rate. As such a side chain-type polymer, the inventors of the present invention have reported polymers comprising, as a side chain group having a π-electron system, carbazole, ferrocene, triphenylamine, pyrene, perylene, an oligothiophene and the like, and have clarified that these polymers are applicable to a cathode material for a secondary cell, a p-mode semiconductor material for a photoelectric transfer device, an electrochromic material and other materials [Synth. Met., 41–43, 3031 (1991), and literatures described therein, for example, Macromolecules, 28, 723 (1995); Synth. Met., 81, 157 (1996); Macromolecules, 30, 380 (1997); Synth. Met., 102, 969 (1999); and Electrochim. Acta, 45, 1543 (2000)]. However, even in the polymer materials described in these literatures, it is difficult to improve heat resistance due to their low glass transition temperature.
In this way, a polymeric material having a high glass transition temperature is required in order to improve heat resistance and mold-processability of an organic EL device.